where did the 70s take the horses
EDIT KK beat me to it
Actually, Rani, "it's both."
Smog controls for certain took their toll. Reduced performance advance curves, leaned out carburetors, and in general, lower compression and diddled cam timing
And you are right "they" changed from gross HP to "net" HP
"Net" is SUPPOSED to be a more relevent representation, taking into account "the actual stuff" that an engine has to have to operate, including alternator, PS pump, water pump etc
BUT THE thing is, "numbers" get "diddled."
My favorite example (and there are many) is ratings on air compressors
"Once upon a time," compressors were rated by the air in cfm that they would output at 90PSI operating pressure
Then in the ?60's? Wards or Sears or someone "discovered" 'HEY' if we rate OURS at 40 psi instead of 90, THE NUMBERS GO UP.
THEN somebody discovered that if you rate them by scfm (suction, or intake, or atmosperic pressure) the numbers REALLY go up
So the very same compressor, at these three different ratings, "seems" bigger at 40 psi, and bigger yet at SCFM than it does at 90 PSI
The point is that "numbers" are only as good, meaningful, and accurate as the guy's ethics who wrote them
Battery ratings, many other things, are a Great Big Lie.